Weight gain is a serious, common side effect of many antipsychotic medications. It is a frequent cause of poor adherence to antipsychotic medications and a major contributor to medical problems including Syndrome X, various cancers, osteoarthritis and sleep apnea. Syndrome X, also called the Metabolic Syndrome, is a constellation of abnormalities of metabolism that confer a high risk of coronary heart disease. Syndrome X includes glucose intolerance, dyslipidemia, hypertension, and central obesity. Long-term patients on antipsychotic medications have markedly increased rates of Syndrome X that are consistent with increased cardiovascular morbidity and decreased life expectancy.